Optical imaging system

ABSTRACT

An optical imaging system includes a first lens having a positive refractive power and a convex object-side surface; a second lens having a negative refractive power, a convex object-side surface, and a concave image-side surface; a third lens having a negative refractive power; a fourth lens having a refractive power; a fifth lens having a negative refractive power; and a sixth lens having a positive refractive power. The first to sixth lenses are sequentially disposed in ascending numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, and are the only lenses having a refractive power in the optical imaging system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/377,343filed on Apr. 8, 2019, now U.S. Pat. No. 11,029,490 issued on Jun. 8,2021, which is a division of application Ser. No. 15/468,312 filed onMar. 24, 2017, now U.S. Pat. No. 10,302,911 issued on May 28, 2019, andclaims the benefit under 35 USC 119(a) of Korean Patent Application Nos.10-2016-0117275 filed on Sep. 12, 2016, and 10-2016-0136720 filed onOct. 20, 2016, in the Korean Intellectual Property Office. The entiredisclosures of application Ser. Nos. 16/377,343 and 15/468,312 andKorean Patent Application Nos. 10-2016-0117275 and 10-2016-0136720 areincorporated herein by reference for all purposes.

BACKGROUND 1. Field

The following description relates to a telephoto imaging systemincluding six lenses.

2. Description of Related Art

A telephoto imaging system for imaging a distant object may have asubstantial size. For example, in a telephoto imaging system, a ratio(TL/f) of an overall imaging system length (TL) with respect to anoverall focal length (f) may be 1 or more. In this case, there arelimitations in mounting a telephoto imaging system in a small electronicdevice such as a mobile terminal, or the like.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

Various examples describe provide an optical imaging system for imaginga distant object, while being mounted in a small terminal.

In accordance with an embodiment, an optical imaging system includeslenses sequentially disposed from an object side of the optical imagingsystem toward an imaging plane of the optical imaging system; and a stopdisposed between a third lens of the lenses and a fourth lens of thelenses, wherein an object-side surface of the third lens is concave, anda ratio TL/f of a distance TL from an object-side surface of a firstlens of the lenses to the imaging plane with respect to an overall focallength f of the optical imaging system is greater than 0.7 and less than1.0.

The first lens may have a positive refractive power, and an object-sidesurface of the first lens may be convex.

A second lens of the lenses may have a negative refractive power, anobject-side surface of the second lens may be convex, and an image-sidesurface of the second lens may be concave.

The third lens may have a negative refractive power, and an object-sidesurface of the third lens may be convex.

An object-side surface of the fourth lens may be convex.

In accordance with an embodiment, an optical imaging system includes afirst lens; a second lens; a third lens; a fourth lens; and a fifthlens, wherein the first lens to the fifth lens each have a refractivepower; a sixth lens having a convex object-side surface; and a stopdisposed between the third lens and the fourth lens.

The optical imaging system may satisfy a Conditional Expression0.7<TL/f<1.0, where TL is a distance from an object-side surface of thefirst lens to an imaging plane, and f is an overall focal length of theoptical imaging system.

The optical imaging system may satisfy a Conditional Expression0.15<R1/f<0.32, where R1 is a radius of curvature of an object-sidesurface of the first lens, and f is an overall focal length of theoptical imaging system.

The optical imaging system may satisfy a Conditional Expression−3.5<f/f2<−0.5, where f is an overall focal length of the opticalimaging system, and f2 is a focal length of the second lens.

The optical imaging system may satisfy a Conditional Expression0.1<d45/TL<0.32, where d45 is a distance from an image-side surface ofthe fourth lens to an object-side surface of the fifth lens, and TL is adistance from an object-side surface of the first lens to an imagingplane.

The optical imaging system may satisfy a Conditional Expression1.6<Nd6<1.75, where Nd6 is a refractive index of the sixth lens.

The optical imaging system may satisfy a Conditional Expression 0.3<tanθ<0.5, where θ is a half angle or field of view of the optical imagingsystem.

The optical imaging system may satisfy a Conditional Expression2.0<f/EPD<2.7, where f is an overall focal length of the optical imagingsystem, and EPD is a diameter of an entrance pupil of the opticalimaging system.

The refractive power of the first lens and a refractive power of thesixth lens may have a same sign.

The refractive power of the second lens and the refractive power of thefifth lens may have a same sign that is different from a sign of therefractive power of the first lens.

An object-side surface of the sixth lens may be convex.

In accordance with an embodiment, an optical imaging system includes afirst lens; a second lens having a convex object-side surface; a thirdlens having a concave image-side surface; a fourth lens having a convexobject-side surface; a fifth lens having a concave object-side surface;and a sixth lens, wherein the first lens has a most convex object-sidesurface among the first to sixth lenses, and the first lens and thefifth lens have a refractive index less than 1.6, and the second lens,the third lens, the fourth lens, and the sixth lens have a refractiveindex equal to or greater than 1.6.

The second lens may have a most concave image-side surface among thefirst to sixth lenses.

The first lens may have a positive refractive power, the second lens mayhave a negative refractive power, the third lens may have a negativerefractive power, the fourth lens may have a positive refractive poweror a negative refractive power, the fifth lens may have a negativerefractive power, and the sixth lens may have a positive refractivepower.

The first lens may have a highest refractive power among the first tosixth lenses, and the sixth lens may have a lowest refractive poweramong the first to sixth lenses.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view of an optical imaging system according to a firstexample.

FIG. 2 illustrates aberration curves of the optical imaging systemillustrated in FIG. 1 .

FIG. 3 is a table listing aspherical characteristics of the lenses ofthe optical imaging system illustrated in FIG. 1 .

FIG. 4 is a view of an optical imaging system according to a secondexample.

FIG. 5 illustrates aberration curves of the optical imaging systemillustrated in FIG. 4 .

FIG. 6 is a table listing aspherical characteristics of the lenses ofthe optical imaging system illustrated in FIG. 4 .

FIG. 7 is a view of an optical imaging system according to a thirdexample.

FIG. 8 illustrates aberration curves of the optical imaging systemillustrated in FIG. 7 .

FIG. 9 is a table listing aspherical characteristics of the lenses ofthe optical imaging system illustrated in FIG. 7 .

FIG. 10 is a rear view of a mobile terminal in which an optical imagingsystem according to an example is mounted.

FIG. 11 is a cross-sectional view of the mobile terminal illustrated inFIG. 10 .

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application. For example, the sequences of operationsdescribed herein are merely examples, and are not limited to those setforth herein, but may be changed as will be apparent after anunderstanding of the disclosure of this application, with the exceptionof operations necessarily occurring in a certain order. Also,descriptions of features that are known in the art may be omitted forincreased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, apparatuses, and/or systems described herein that will beapparent after an understanding of the disclosure of this application.

As used herein, the term “and/or” includes any one and any combinationof any two or more of the associated listed items.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various members, components, regions, layers, or sections,these members, components, regions, layers, or sections are not to belimited by these terms. Rather, these terms are only used to distinguishone member, component, region, layer, or section from another member,component, region, layer, or section. Thus, a first member, component,region, layer, or section referred to in examples described herein mayalso be referred to as a second member, component, region, layer, orsection without departing from the teachings of the examples.

Spatially relative terms such as “above,” “upper,” “below,” and “lower”may be used herein for ease of description to describe one element'srelationship to another element as shown in the figures. Such spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. For example, if the device in the figures is turned over,an element described as being “above” or “upper” relative to anotherelement will then be “below” or “lower” relative to the other element.Thus, the term “above” encompasses both the above and below orientationsdepending on the spatial orientation of the device. The device may alsobe oriented in other ways (for example, rotated 90 degrees or at otherorientations), and the spatially relative terms used herein are to beinterpreted accordingly.

The terminology used herein is for describing various examples only, andis not to be used to limit the disclosure. The articles “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. The terms “comprises,” “includes,”and “has” specify the presence of stated features, numbers, operations,members, elements, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, operations,members, elements, and/or combinations thereof.

Due to manufacturing techniques and/or tolerances, variations of theshapes shown in the drawings may occur. Thus, the examples describedherein are not limited to the specific shapes shown in the drawings, butinclude changes in shape that occur during manufacturing.

The features of the examples described herein may be combined in variousways as will be apparent after an understanding of the disclosure ofthis application. Further, although the examples described herein have avariety of configurations, other configurations are possible as will beapparent after an understanding of the disclosure of this application.

In accordance with an example, a first lens refers to a lens closest toan object or a subject of which an image is captured. A sixth lens is alens closest to an imaging plane or an image sensor. In the presentspecification, all radii of curvature of lenses, thicknesses of thelenses and other elements, gaps between the lenses and other elements,an overall length of the optical imaging system, i.e., a distance froman object-side surface of the first lens to the imaging plane (TL), ahalf diagonal length of the imaging plane (IMG HT), focal lengths of thelenses, and an overall focal length of the optical imaging system (f)are indicated in millimeters (mm). However, other units of measurementmay be used. Further, the thicknesses of the lenses and other elements,the gaps between the lenses and other elements, and TL are measuredalong an optical axis of the optical imaging system.

A surface of a lens being convex means that an optical axis portion of acorresponding surface is convex, and a surface of a lens being concavemeans that an optical axis portion of a corresponding surface isconcave. Therefore, in a configuration in which one surface of a lens isdescribed as being convex, an edge portion of the lens may be concave.Likewise, in a configuration in which one surface of a lens is describedas being concave, an edge portion of the lens may be convex. In otherwords, a paraxial region of a lens may be convex, while the remainingportion of the lens outside the paraxial region is either convex,concave, or flat. Further, a paraxial region of a lens may be concave,while the remaining portion of the lens outside the paraxial region iseither convex, concave, or flat.

In addition, in an embodiment, thicknesses and radii of curvatures oflenses are measured in relation to optical axes of the correspondinglenses.

An optical imaging system includes six lenses. For example, the opticalimaging system may include a first lens, a second lens, a third lens, afourth lens, a fifth lens, and a sixth lens sequentially disposed froman object side to an image side. In another example, the optical imagingsystem may include from four lenses up to six lenses without departingfrom the scope of the embodiments herein described. Although embodimentsof the optical imaging system described herein include six lenses with arefractive power, a person of ordinary skill in the relevant art willappreciate that the number of lenses in the optical imaging system mayvary, for example, between two to six lenses, while achieving thevarious results and benefits described hereinbelow. Also, although eachlens is described as having a particular refractive power, a differentrefractive power for at least one of the lenses may be used to achievethe intended result.

The first lens has a refractive power. For example, the first lens has apositive refractive power. At least one surface of the first lens isconvex. For example, an object-side surface of the first lens is convex.

The first lens has an aspherical surface. For example, both surfaces ofthe first lens are aspherical. The first lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.For example, the first lens may be formed of a plastic material or apolyurethane material. However, a material of the first lens is notlimited to being a plastic material. For example, the first lens may beformed of a glass material. The first lens has a low refractive index.For example, the refractive index of the first lens is lower than 1.6.

The second lens has a refractive power. For example, the second lens hasa negative refractive power. One surface of the second lens is convex.For example, an object-side surface of the second lens is convex.

The second lens has an aspherical surface. For example, an object-sidesurface of the second lens is aspherical. The second lens is formed of amaterial having a high degree of light transmissivity and excellentworkability. For example, the second lens is formed of a plasticmaterial or a polyurethane material. However, a material of the secondlens is not limited to being plastic. For example, the second lens maybe formed of a glass material. The second lens has a refractive indexhigher than that of the first lens. For example, the refractive index ofthe second lens is 1.6 or more.

The third lens has a refractive power. For example, the third lens has anegative refractive power. At least one surface of the third lens isconcave. For example, an object-side surface of the third lens isconcave.

The third lens has an aspherical surface. For example, an image-sidesurface of the third lens is aspherical. The third lens is formed of amaterial having a high degree of light transmissivity and excellentworkability. For example, the third lens may be formed of a plasticmaterial or a polyurethane material. However, a material of the thirdlens is not limited to being plastic. For example, the third lens may beformed of a glass material. The third lens has a refractive index higherthan that of the first lens. For example, a refractive index of thethird lens is 1.6 or more.

The fourth lens has a refractive power. For example, the fourth lens hasa positive refractive power or a negative refractive power. At least onesurface of the fourth lens is convex. For example, an object-sidesurface of the fourth lens is convex.

The fourth lens has an aspherical surface. For example, both surfaces ofthe fourth lens are aspherical. The fourth lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.For example, the fourth lens may be formed of a plastic material or apolyurethane material. However, a material of the fourth lens is notlimited to being plastic. For example, the fourth lens may be formed ofa glass material. The fourth lens has a refractive index higher thanthat of the first lens. For example, a refractive index of the fourthlens is 1.6 or more.

The fifth lens has a refractive power. For example, the fifth lens has anegative refractive power. At least one surface of the fifth lens isconcave. For example, both surfaces of the fifth lens are concave.

The fifth lens has an aspherical surface. For example, both surfaces ofthe fifth lens are aspherical. The fifth lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.For example, the fifth lens may be formed of a plastic material or apolyurethane material. However, a material of the fifth lens is notlimited to being plastic. For example, the fifth lens may be formed of aglass material. The fifth lens has a refractive index substantially thesame as that of the first lens. For example, a refractive index of thefifth lens is less than 1.6.

The sixth lens has a refractive power. For example, the sixth lens has apositive refractive power. At least one surface of the sixth lens isconvex. For example, an image-side surface of the sixth lens is convex.The sixth lens has an inflection point. For example, the sixth lens hasone or more inflection points formed on both surfaces thereof.

The sixth lens has an aspherical surface. For example, both surfaces ofthe sixth lens may be aspherical. The sixth lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.For example, the sixth lens may be formed of a plastic material or apolyurethane material. However, a material of the sixth lens is notlimited to being plastic. For example, the sixth lens may be formed of aglass material. The sixth lens has a refractive index higher than thatof the first lens. For example, a refractive index of the sixth lens maybe 1.6 or more.

In accordance with other embodiments, each or at least one of the firstthrough sixth lenses may be configured in an opposite refractive powerfrom the configuration described above. For example, in an alternativeconfiguration, the first lens has a negative refractive power, thesecond lens has a positive refractive power, the third lens has apositive refractive power, the fourth lens has a negative refractivepower, the fifth lens has a positive refractive power, and the sixthlens has a negative refractive power.

An aspherical surface of each of the first lens to the sixth lens may berepresented by Equation 1 below.

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18} + {Jr}^{20}}} & (1)\end{matrix}$

In Equation 1, c is an inverse of a radius of curvature of the lens, kis a conic constant, r is a distance from a certain point on anaspherical surface of the lens to an optical axis, A to J are asphericalconstants, and Z (or SAG) is a distance between the certain point on theaspherical surface of the lens at the distance r and a tangential planemeeting the apex of the aspherical surface of the lens.

An optical imaging system may further include a filter, an image sensor,and a stop.

The filter may be disposed between the sixth lens and the image sensor.The filter blocks some wavelengths of light to obtain a clear image. Forexample, the filter may block an infrared wavelength of light. Thefilter has a predetermined refractive index. For example, the filter mayhave a refractive index of 1.53 or less. In addition, the filter has apredetermined Abbe number. For example, the filter may have an Abbenumber of 40 or less.

The image sensor forms an imaging plane. For example, a surface of theimage sensor may form an imaging plane.

The stop is disposed to adjust an amount of light incident on a lens.For example, the stop is disposed between the third lens and the fourthlens.

The optical imaging system satisfies the following ConditionalExpressions:

0.7 < TL/f < 1.0 (Conditional Expression 1) 0.15 < R1/f < 0.32(Conditional Expression 2) −3.5 < f/f2 < −0.5 (Conditional Expression 3)0.1 < d45/TL < 0.7 (Conditional Expression 4) 1.6 < Nd6 < 1.75(Conditional Expression 5) 0.3 < tan θ < 0.5 (Conditional Expression 6)2.0 < f/EPD < 2.7 (Conditional Expression 7)

In the Conditional Expressions, TL is a distance from an object-sidesurface of the first lens to an imaging plane, f is an overall focallength of the optical imaging system, and f2 is a focal length of thesecond lens. Furthermore, R1 is a radius of curvature of the object-sidesurface of the first lens, d45 is a distance from an image-side surfaceof the fourth lens to an object-side surface of the fifth lens, Nd6 is arefractive index of the sixth lens, θ is a half angle or field of view(HFOV) of the optical imaging system, and EPD is a diameter of anentrance pupil of the optical imaging system.

Conditional Expression 1 specifies a condition for miniaturization ofthe optical imaging system. For example, in a case in which an opticalimaging system is outside of an upper limit value of ConditionalExpression 1, there may be limitations on the miniaturization thereof,thus, making it difficult to mount such an optical imaging system in aportable terminal. In addition, in a case in which an optical imagingsystem is outside of a lower limit value of Conditional Expression 1,there may be limitations in the manufacturing of the optical imagingsystem.

Conditional Expression 2 specifies a condition for manufacturing a firstlens to configure a telephoto imaging system. For example, in a case inwhich a first lens is outside of an upper limit value of ConditionalExpression 2, a longitudinal spherical aberration is increased and afocal length of the optical imaging system is short. In a case in whicha first lens is outside of a lower limit value of Conditional Expression2, a focal length of the optical imaging system is increased, but theremay be limitations on the manufacturing thereof. In addition, in a casein which a first lens is outside of a lower limit value of ConditionalExpression 2, a thickness of an edge portion of a lens may be thinner,thus, producing limitations on the manufacturing thereof.

Conditional Expression 3 specifies a design condition of the second lensfor implementing an optical imaging system having a high degree ofresolution. For example, in a case in which a second lens is outside ofthe numerical range of Conditional Expression 3, astigmatic aberrationof the optical imaging system is increased to cause degradation of animage.

Conditional Expression 4 specifies a design condition for configuring atelephoto imaging system. For example, in a case in which an opticalimaging system is outside of a lower limit value of ConditionalExpression 4, since a focal length is short, there are limitations inusing such an optical imaging system for telephoto purposes. In a casein which an optical imaging system is outside of an upper limit value ofConditional Expression 4, because an overall length TL of the opticalimaging system is increased, there may be limitations on theminiaturization thereof.

Conditional Expression 5 specifies a design condition of a fifth lensfor an optical imaging system having a high degree of resolution. Forexample, in a case in which a fifth lens satisfying the numerical rangeof Conditional Expression 5 has a low Abbe number of 25 or less, thereis an advantage in correcting astigmatic aberrations, longitudinalchromatic aberrations, and magnification aberrations.

Conditional Expression 6 specifies a range of a half angle or field ofview (HFOV) for configuring a telephoto imaging system, whileConditional Expression 7 specifies the numerical range of an f-numberfor an optical imaging system having a high degree of resolution.

In an optical imaging system, lenses may be disposed in a predeterminedorder depending on refractive power thereof (an absolute value of aninverse number of a focal length). As an example, refractive power of anodd-numbered lens is greater than that of refractive power of aneven-numbered lens disposed on an image-side surface. In other words,refractive power of the first lens is greater than refractive power ofthe second lens, refractive power of the third lens is greater thanrefractive power of the fourth lens, and refractive power of the fifthlens is greater than refractive power of the sixth lens.

In the optical imaging system, a lens having the highest refractivepower is a lens closest to an object, and a lens having the lowestrefractive power is a lens closest to an imaging plane or an imagesensor. For example, in the optical imaging system, the first lens hasthe highest refractive power, and the fourth lens or the sixth lens hasthe lowest refractive power.

In the optical imaging system, in accordance with an embodiment, thefirst lens has the most convex surface or the most convex contour of anyof the lenses. For example, an object-side surface of the first lens hasthe most convex surface of all of the lenses. In other words, the firstlens has a shortest or smallest radius of curvature from the opticalaxis of all the lenses included in the optical imaging system, thus,having a largest convex object-side surface in the optical imagingsystem.

In the optical imaging system, the second lens has the most concavesurface or the most concave contour of any of the lenses. For example,an image-side surface of the second lens has the most concave surface ofall of the lenses. In other words, the second lens has a greatest radiusof curvature from the optical axis of all the lenses included in theoptical imaging system, thus, having a largest concave image-sidesurface in the optical imaging system.

In the optical imaging system, the fourth lens has a substantially flatsurface. For example, an image-side surface of the fourth lens has ashape close to planar. In the optical imaging system, three or moreneighboring lenses have refractive indices substantially similar to eachother. For example, the second lens to the fourth lens has substantiallythe same or similar refractive indices. The refractive indices of thesecond lens to the fourth lens may be selected within the range of 1.63to 1.68.

Focal lengths of lenses forming the optical imaging system may beselected within a predetermined range. For example, a focal length ofthe first lens is selected within the range of 2.4 mm to 3.1 mm, a focallength of the second lens is selected within the range of −8.5 mm to−5.8 mm, a focal length of the third lens is selected within the rangeof −11.5 mm to −3.8 mm, a focal length of the fifth lens is selectedwithin the range of −4.7 mm to −3.7 mm, and a focal length of the sixthlens is selected within the range of 9.0 mm to 13.5 mm.

Next, optical imaging systems according to several examples will bedescribed.

FIG. 1 is a view of an optical imaging system according to a firstexample.

An optical imaging system 100 includes a first lens 110, a second lens120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixthlens 160.

The first lens 110 has a positive refractive power, and both surfacesthereof are convex. The second lens 120 has a negative refractive power,an object-side surface thereof is convex, and an image-side surfacethereof is concave. The third lens 130 has a negative refractive power,and both surfaces thereof are concave. The fourth lens 140 has apositive refractive power, and both surfaces thereof are convex. Thefifth lens 150 has a negative refractive power, and both surfacesthereof are concave. In addition, the fifth lens 150 has an inflectionpoint formed on both surfaces. The sixth lens 160 has a positiverefractive power, and both surfaces thereof are convex. In addition, thesixth lens 160 has an inflection point formed on an object-side surfaceor an image-side surface.

The first lens 110, among the lenses, has the highest refractive power,while the sixth lens 160 has the lowest refractive power.

The optical imaging system 100 may further include a filter 170, animage sensor 180, and a stop ST. The filter 170 is disposed between thesixth lens 160 and the image sensor 180, and the stop ST is disposedbetween the third lens 130 and the fourth lens 140.

FIG. 2 illustrates aberration curves of the optical imaging system 100illustrated in FIG. 1 , and FIG. 3 is a table listing asphericalcharacteristics of the lenses of the optical imaging system 100illustrated in FIG. 1 .

Table 1 below lists characteristics of the optical imaging system 100illustrated in FIG. 1 .

TABLE 1 First Example HFOV = 23.797 f = 5.997 TL = 5.391 Surface Radiusof Thickness/ Focal Refractive Abbe # Element Curvature Distance LengthIndex # S1 1st lens 1.5100 0.9130  2.750 1.544 56.1 S2 −323.8700 0.1300S3 2nd lens 6.2200 0.2400 −6.460 1.661 20.3 S4 2.5100 0.3320 S5 3rd lens−7.1600 0.2400 −4.260 1.650 21.5 S6 4.6600 0.0500 S7 Stop infinity0.0100 S8 4th lens 4.6400 0.2400  6.900 1.650 21.5 S9 −200.0000 1.2210S10 5th lens −2.7300 0.2900 −4.230 1.544 56.1 S11 15.7300 0.1500 S12 6thlens 17.1800 0.6980 10.310 1.650 21.5 S13 −11.0100 0.5000 S14 Filterinfinity 0.1100 1.523 39.1 S15 infinity 0.2670 S16 Imaging infinityplane

FIG. 4 is a view of an optical imaging system according to a secondexample.

An optical imaging system 200 includes a first lens 210, a second lens220, a third lens 230, a fourth lens 240, a fifth lens 250, and a sixthlens 260.

The first lens 210 has a positive refractive power, and both surfacesthereof are convex. The second lens 220 has a negative refractive power,an object-side surface thereof is convex, and an image-side surfacethereof is concave. The third lens 230 has a negative refractive power,and both surfaces thereof are concave. The fourth lens 240 has apositive refractive power, and both surfaces thereof are convex. Thefifth lens 250 has a negative refractive power, and both surfacesthereof are concave. In addition, the fifth lens 250 has an inflectionpoint formed on both surfaces. The sixth lens 260 has a positiverefractive power, and both surfaces thereof are convex. In addition, thesixth lens 260 has an inflection point formed on at least one surface.

In one configuration and as illustrated in FIG. 4 , endpoints of thefifth lens 250 extend, along an optical axis, toward the object sidesurface, covering (at end portions of the first through fourth lenses210 through 240, where the end portions are positioned perpendicular tothe optical axis) the first lens 210, the second lens 220, the thirdlens 230, and the fourth lens 240. Although the fifth lens 250 isillustrated as extending the endpoints thereof, at ends after inflectionpoints, which are positioned at end portions of the object-side surfaceof the fifth lens 250, the fifth lens 250 may extend to only cover someof the second through fourth lenses 210 through 240. Also, the endpointsof the fifth lens 250 extend towards the object-side, covering endportions of the lenses 210 through 240, with or without contacting theend portions of the lenses 210 through 240.

The first lens 210, among the lenses, has the highest refractive power,and the sixth lens 260 has the lowest refractive power.

The optical imaging system 200 includes a filter 270, an image sensor280, and a stop ST. The filter 270 is disposed between the sixth lens260 and the image sensor 280, and the stop ST is disposed between thethird lens 230 and the fourth lens 240.

FIG. 5 illustrates aberration curves of the optical imaging system 200illustrated in FIG. 4 , and FIG. 6 is a table listing asphericalcharacteristics of the lenses of the optical imaging system 200illustrated in FIG. 4 .

Table 2 below lists characteristics of the optical imaging system 200illustrated in FIG. 4 .

TABLE 2 Second Example HFOV = 23.797 f = 6.001 TL = 5.655 Surface Radiusof Thickness/ Focal Refractive Abbe # Element Curvature Distance LengthIndex # S1 1st lens 1.5100 0.9090  2.760 1.544 56.1 S2 −4974.2600 0.1210S3 2nd lens 6.6100 0.2400 −6.960 1.661 20.3 S4 2.6900 0.3430 S5 3rd lens−5.1000 0.2400 −5.300 1.650 21.5 S6 11.2400 0.0180 S7 Stop infinity0.0700 S8 4th lens 6.9800 0.2400 10.590 1.650 21.5 S9 −2000.0000 1.2040S10 5th lens −2.9900 0.2900 −4.230 1.544 56.1 S11 10.6000 0.1290 S12 6thlens 17.5600 0.7090 11.500 1.650 21.5 S13 −13.0700 0.5000 S14 Filterinfinity 0.1100 1.523 39.1 S15 infinity 0.2660 S16 Imaging infinity0.2660 plane

FIG. 7 is a view of an optical imaging system according to a thirdexample.

An optical imaging system 300 includes a first lens 310, a second lens320, a third lens 330, a fourth lens 340, a fifth lens 350, and a sixthlens 360.

In the third example, the first lens 310 has a positive refractivepower, an object-side surface thereof is convex, and an image-sidesurface thereof is concave. The second lens 320 has a negativerefractive power, an object-side surface thereof is convex, and animage-side surface thereof is concave. The third lens 330 has a negativerefractive power, an object-side surface thereof is concave, and animage-side surface thereof is convex. The fourth lens 340 has a negativerefractive power, an object-side surface thereof is convex, and animage-side surface thereof is concave. The fifth lens 350 has a negativerefractive power, and both surfaces thereof are concave. In addition,the fifth lens 350 has an inflection point formed on both surfaces. Thesixth lens 360 has a positive refractive power, and both surfacesthereof are convex. In addition, the sixth lens 360 has an inflectionpoint formed on at least one surface.

In one configuration and as illustrated in FIG. 7 , endpoints of thefifth lens 250 extend, along an optical axis, toward the object sidesurface, covering (at end portions of the second through fourth lenses320 through 340, where the end portions are positioned perpendicular tothe optical axis) the second lens 320, the third lens 330, and thefourth lens 340. Also, the endpoints of the fifth lens 350 extendtowards the object-side, covering end portions of the lenses 320 through340, with or without contacting the end portions of the lenses 320through 340.

The optical imaging system 300 includes a filter 370, an image sensor380, and a stop ST. The filter 370 is disposed between the sixth lens360 and the image sensor 380, and the stop ST is disposed between thethird lens 330 and the fourth lens 340.

The first lens 310 of the lenses has the highest refractive power, andthe fourth lens 340 has the lowest refractive power.

FIG. 8 illustrates aberration curves of the optical imaging system 300illustrated in FIG. 7 , and FIG. 9 is a table listing asphericalcharacteristics of the optical imaging system 300 illustrated in FIG. 7.

Table 3 below lists characteristics of the optical imaging system 300illustrated in FIG. 7 .

TABLE 3 Third Example HFOV = 23.797 f = 6.001 TL = 5.395 Surface Radiusof Thickness/ Focal Refractive Abbe # Element Curvature Distance LengthIndex # S1 1st lens 1.4900 0.8910  2.770 1.544 56.1 S2 65.7500 0.1210 S32nd lens 13.0600 0.2400 −7.690 1.661 20.3 S4 3.6600 0.3010 S5 3rd lens−4.9600 0.2400 −10.430 1.650 21.5 S6 −18.2300 0.0070 S7 Stop infinity0.1000 S8 4th lens 20000.0 0.2400 −18899.980   1.650 21.5 S9 7663.751.1820 S10 5th lens −3.1200 0.2900 −4.250 1.544 56.1 S11 9.3600 0.1890S12 6th lens 18.6100 0.7130 12.030 1.650 21.5 S13 −13.5400 0.5000 S14Filter infinity 0.1100 1.523 39.1 S15 infinity 0.2710 S16 Imaginginfinity plane

Table 4 below lists values of Conditional Expressions 1 to 7 for theoptical imaging systems according to the first to third examples.

TABLE 4 Conditional First Second Third Expression Example ExampleExample TL/f 0.899 0.898 0.899 R1/f 0.251 0.252 0.248 f/f2 −0.928 −0.862−0.781 d45/TL 0.226 0.223 0.219 Nd6 1.650 1.650 2.650 tan θ 0.441 0.4410.441 f/EPD 2.480 2.488 2.590

FIG. 10 is a rear view of a mobile terminal in which an optical imagingsystem according to an example is mounted, and FIG. 11 is across-sectional view of the mobile terminal illustrated in FIG. 10 .

A mobile terminal 10 includes a plurality of camera modules, a firstcamera module 20 and a second camera module 30. The first camera module20 includes a first optical imaging system 101 configured to image anear subject, and the second camera module 30 includes a second opticalimaging system 100, 200, or 300 configured to image a distant subject.

The first optical imaging system 101 includes a plurality of lenses. Forexample, the first optical imaging system 101 includes four or morelenses. The first optical imaging system 101 may be configured tointegrally image objects located at a short distance. For example, thefirst optical imaging system 101 has a wide angle or field of view of 50degrees or more, and a TL/f ratio is 1.0 or more.

The second optical imaging system 100, 200, or 300 includes a pluralityof lenses. For example, the second optical imaging system 100, 200, or300 includes six lenses. The second optical imaging system 100, 200, or300 is one of the optical imaging systems, according to the firstexample to the third example, described previously. The second opticalimaging system 100, 200, or 300 is configured to image an object locateddistantly. For example, the second optical imaging system 100, 200, or300 has an angle or field of view of 40 degrees or less, and an L/fratio is less than 1.0.

The first optical imaging system 101 and the second optical imagingsystem 100, 200, or 300 may have the substantially the same size. Forexample, an overall length L1 of the first optical imaging system 101 issubstantially the same as an overall length L2 of the second opticalimaging system 100, 200, or 300. Alternatively, a ratio L1/L2 of theoverall length L1 of the first optical imaging system 101 with respectto the overall length L2 of the second optical imaging system 100, 200,or 300 is 0.8 to 1.0. Alternatively, a ratio L2/h of the overall lengthL2 of the second optical imaging system 100, 200, or 300 with respect toa thickness of the mobile terminal 10 is 0.8 or less.

As set forth above, according to examples, an optical imaging system forimaging a distant object while being mounted on a small terminal.

While this disclosure includes specific examples, it will be apparent toone of ordinary skill in the art that various changes in form anddetails may be made in these examples without departing from the spiritand scope of the claims and their equivalents. The examples describedherein are to be considered in a descriptive sense only, and not forpurposes of limitation. Descriptions of features or aspects in eachexample are to be considered as being applicable to similar features oraspects in other examples. Suitable results may be achieved if thedescribed techniques are performed in a different order, and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner, and/or replaced or supplemented by othercomponents or their equivalents. Therefore, the scope of the disclosureis defined not by the detailed description, but by the claims and theirequivalents, and all variations within the scope of the claims and theirequivalents are to be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system comprising: a firstlens having a positive refractive power and a convex object-sidesurface; a second lens having a negative refractive power and a concaveimage-side surface; a third lens having a negative refractive power anda focal length in a range of −11.5 mm to −3.8 mm; a fourth lens having arefractive power; a fifth lens having a negative refractive power; and asixth lens having a positive refractive power, wherein the first tosixth lenses are sequentially disposed in ascending numerical order froman object side of the optical imaging system toward an imaging plane ofthe optical imaging system, the first to sixth lenses are the onlylenses having a refractive power in the optical imaging system, and aradius of curvature of an object-side surface of the fourth lens isgreater than a radius of curvature of the image-side surface of thesecond lens.
 2. The optical imaging system of claim 1, wherein the firstlens has a convex image-side surface.
 3. The optical imaging system ofclaim 1, wherein the third lens has a concave image-side surface.
 4. Theoptical imaging system of claim 1, wherein the object-side surface ofthe fourth lens is convex.
 5. The optical imaging system of claim 1,wherein the fifth lens has a concave object-side surface.
 6. The opticalimaging system of claim 1, wherein the fifth lens has a concaveimage-side surface.
 7. The optical imaging system of claim 1, whereinthe sixth lens has a convex image-side surface.
 8. The optical imagingsystem of claim 1, wherein the optical imaging system further satisfiesthe following conditional expression:0.7<TL/f<1.0 where TL is a distance from the object-side surface of thefirst lens to the imaging plane, and f is an overall focal length of theoptical imaging system.
 9. The optical imaging system of claim 1,wherein the optical imaging system further satisfies the followingconditional expression:0.15<R1/f<0.32 where R1 is a radius of curvature of the object-sidesurface of the first lens, and f is an overall focal length of theoptical imaging system.
 10. The optical imaging system of claim 1,wherein the optical imaging system further satisfies the followingconditional expression:−3.5<f/f2<−0.5 where f is an overall focal length of the optical imagingsystem, and f2 is a focal length of the second lens.
 11. The opticalimaging system of claim 1, wherein the optical imaging system furthersatisfies the following conditional expression:0.1<d45/TL<0.32 where d45 is a distance from an image-side surface ofthe fourth lens to an object-side surface of the fifth lens, and TL is adistance from the object-side surface of the first lens to the imagingplane.
 12. The optical imaging system of claim 1, wherein the opticalimaging system further satisfies the following conditional expression:1.6<Nd6<1.75 where Nd6 is a refractive index of the sixth lens.
 13. Theoptical imaging system of claim 1, wherein the optical imaging systemfurther satisfies the following conditional expression:2.0<f/EPD<2.7 where f is an overall focal length of the optical imagingsystem, and EPD is a diameter of an entrance pupil of the opticalimaging system.
 14. An optical imaging system comprising: a first lenshaving a positive refractive power and a convex object-side surface; asecond lens having a negative refractive power and a concave image-sidesurface; a third lens having a negative refractive power and a focallength in a range of −11.5 mm to −3.8 mm; a fourth lens having arefractive power; a fifth lens having a negative refractive power; and asixth lens having a positive refractive power, wherein the first tosixth lenses are sequentially disposed in ascending numerical order froman object side of the optical imaging system toward an imaging plane ofthe optical imaging system, the first to sixth lenses are the onlylenses having a refractive power in the optical imaging system, and thesixth lens has a convex object-side surface.